Hydraulically controlled differential web tensioning mechanism



May 1958 R. LE B BOWEN, JR 2,835,454

HYDRAULICALLY CONTROLLED DIFFERENTIAL E WEB TENSIONING MECHANISM Filed Feb. 4, 1954 INVENTOR. RICHARD LBARON BOWEN:

BY 31% EM JIM ATTORNEY ly by the pump to the nited States Patent HYDRAULICALLY CONTROLLED DIFFERENTIAL This invention relates to web tensioning mechanisms and more particularly to a hydraulically'controlled differential. operatively connected to a web tensioning mechanism.

One of the objects of the present inventionis to provide a constant tension on a web through a hydraulically controlled differential gear train'.

Another .object of the present invention is to provide a constant tension on a web while eliminating mechanically operating braking mechanisms and manually operated braking mechanisms.

Still another object of this invention is to transmit a large part of the initial operating power back to the original drive while using a very small percentage of the initial power in the hydraulic control, making possible the utilization of an extremely small hydraulic pump and hydraulic motor when compared to the size of hydraulic pump and motor needed when all the power is transmitted hydraulically.

And still another object ofthe present invention is to provide a smoothly operating constant tension web mechanism operating at a constant linear speed.

Other objects of the present invention will be pointed out in part and become apparent in part in the following specification and claims.

The present invention is. an improvement over U. S. Patent #2,164,596. It relates to machines which process web materials such as cloth, paper,'cellophane, metal foil and the like in which constant tension is a prerequisite to a satisfactory product. Tension has heretofore been maintained upon the web in various ways. One of which is to fix the parent roll upona shaft and to apply a brake load to the shaft. Since the parent roll decreases in diameter as the web isunwound therefrom and since at a given brake, load the tension on the web is proportional to the radius of the roll; it is necessary to continually adjust the brake as the web is unwound from the parent roll. In addition to the expense of providing an attendant whose sole duty is to adjust the brake, there is a very large amount of power wasted at thebrake. Also, the energy dissipated through the brake causes the brake to overheat and the brake lining to 'rapidly burn out even with a coolant flowing over or through the brake.

The present inventionobviates these disadvantages by providing a control which automatically functions at constant speed.

The problem is solved in said Patent #2,164,596 by passing the web from the unwinding roll over a roller which drives a hydraulic pump. The pump in turn drives a hydraulic motor which applies the power provided by the roller to the main machine drive. A deficiency of this arrangement is that full power is transmitted hydraulicalmotor. transmits the greater portion of main drive directly through gears, and only a small fraction of the power hydraulically from pump to motor, thereby reducing the size of the hydraulic pump and the power back to the The present invention ice required.

Referring to the drawings wherein like reference characters refer to like parts:

Figure 1 is a diagrammatic plan view partly in section of the new and improved hydraulically controlled differential web tensioning mechanism.

Figure 2 is a modified form of Figure 1.

According to the invention in its general aspect, a Web of material is withdrawn from a parent roll of material at a constant linear speed. The web drives a dragging roller secured to the input shaft of a differential gear train. The output shaft of the differential gear train drives pull rollers so that power is returned to the input shaft.

Tension is applied to the web by controlling the torque applied to the idler shaft of the differential gear train by the hydraulic system.

Referring to Figure 1 of the drawings, web 11 is withdrawn from parent roll 12 by means of pull or feed rollers 13, 14. Pull roller 13 is driven by an electric motor 15. Through frictional contact pull roller 13 drives pull roller 14.. Web 11 is wound upon beam 16 which is driven by motor 15 through slipping belt 17. The web 11 passes between the bite of a pair of drag rollers 21, 22 which are driven by the pull of the web.

A differential gear train generally indicated by reference character 22, comprises an input shaft 23, an output shaft 24. and an idler shaft 25, all rotatively mounted in a casing 26 or reservoir. with elongated hubs, are rotatively mounted on idler shaft 25 for independent rotation thereon.

Bevel gears 30 and 33 which are in engagement with bevel'gears 32 .and 33, are journalled to stub axles 27, 27A respectively, which form part of a carrier 19 secured to idler shaft 25. A sprocket 34 is secured to the elongatedhub of bevel input shaft 23. A

r chain 40 operatively connects sprocket 41 with sprocket 34. A sprocket 35 is secured to the elongated hub of bevel gear 33. A sprocket 37 is secured.

to output shaft 24. A chain 36 operatively connects sprocket 35 with sprocket 37.

It will be seen that, if the input shaft 23 and the output shaft 24 are turning at the same velocity but in op- 44 and 48 are journalled in casing 26. A spur gear 47 meshing with spur gear 46 is fixed to spindle 48. A spur.

gear 43 fixed to spindle 4-4- meshes with spur gear 42.

A hydraulic pump 45- fixed to casing 26 is operativelyconnected to spindle 44. A hydraulic motor 50 fixed to casing 26 is operatively connected to spindle 48. They are well known inthe art.

Hydraulic pump 45 draws hydraulic fluid from the bottom of casing 26 throughconduit 51 and discharges hydraulic fluid to hydraulic motor 50 through conduit 52' which is provided with a pressure gage 49 and a throttle valve 55. Hydraulic motor 5th returns hydraulic fluid to casing 26 through conduit 53. A bleed line or conduit 54 connects throttle valve 55 with casing 26. I

Output shaft 24 is provided through a coupling 67. A bevel pinion 65 is secured to the end of shaft extension 66 and meshes with a'bevel gear 64 secured to axle 68 to cured.

Input shaft 23 is provided with a shaft extension 62 through a coupling 63. A bevel pinion 61 is secured to Bevel gears 32 and 33 providedgear 32. A sprocket 41 is secured to greater than that a spur gear 42 is fixed to idler shaft 25. I is fixed to output shaft 24. Two spindles with ashaft extension 66 which pull roller 14 is .se-'

3 the end of shaft extension 62 and meshes with a bevel gear 60 secured to axle 69 to which drag roller 21 is secured.

In operation, electric motor is started, thereby driving pull roller 13 and through frictional contact pull roller 14 is driven. Pull rollers 13, 14 draw web 11 from parent roll 12. Web 11 is wound upon beam 16 which is being rotated by motor 15 through slip belt 17.

The differential gear train 22 connecting input shaft 23 and output shaft 24 is designed so that when web 11 is withdrawn from parent roll 12 by pull rollers 13 and 14 passing between the bite of drag rollers and 21 and wound upon beam 16, bevel gear 32 driven through sprocket 34, chain 40, sprocket 41, input shaft 23, etc., will revolve at a speed faster than bevel gear 3?: driving sprocket 35, chain 36, sprocket 37, output shaft 24 etc. This produces rotation in idler shaft 25 equal to one half the difference in speed between input shaft 23 and output shaft 24. Rotation of idler shaft 25 actuates hydraulic pump through spindle 44 and spur gears 43 and 42. Hydraulic pump 45 draws hydraulic fluid from the reservoir in the bottom of casing 26. The hydraulic fluid discharged from hydraulic pump 45 drives hydraulic motor 50. Pressure gage 49 gives the reading of the pressure of the discharged hydraulic fluid passing from hydraulic pump 45 to hydraulic motor 50.

The displacement of hydraulic pump 45 per unit of time is greater than the displacement of hydraulic motor 50 per unit of time. The excess hydraulic fluid is exhausted through bleed line 54 and throttle valve Hydraulic motor 50 can only turn at the speed permitted by pull roller 14 because it is controlled by spindle 48, spur gears 47, 46 etc., driven by electric motor 15. Thus, throttle valve 55 controls the pressure of the hydraulic fluid delivered by hydraulic pump 45 and therefore controls the torque applied to idler shaft 25 by the hydraulic system. The torque applied to idler shaft 25 determines the torque exerted by input shaft 23 and thus determines the drag produced by drag rollers 20 and 21. Therefore, the tension on web 11 between pull rollers 13, 14 and drag rollers 20, 21 is controlled by throttle valve 55 and the relative value of the tension is shown on pressure gage 49.

It is obvious that tensions can be duplicated quite accurately by means of pressure gage 49. It is also apparent that the power required to produce the tension is not thrown away, but rather is put back into pull roller 14, thereby causing motor 15 to do less work. The power to produce the tension on web 11 is transmitted directly from input shaft 23 to output shaft 24 through sprockets 41, 34,. chain 40, gears 30, 31, 32, 33, sprockets 35, 37 and chain 36. It is also transmitted indirectly from input shaft 23 to output shaft 24 through hydraulic pump 45 and hydraulic motor 50.

Assume as a specific example that in operation bevel gear 32 revolves at 1000 R. P. M. and bevel gear 33 revolves at 900 R. P. M. Then idler shaft 25 will revolve at 50 R. P. M. In this case ninety percent of the power is transmitted by direct drive from input shaft 23 to output shaft 24, and only ten percent of the power is transmitted by hydraulic power through hydraulic pump 45 and hydraulic motor 50, neglecting the power loss through bleed line 54. Thus the size of the hydraulic equipment in this case is ,4 the size of a direct hydraulic drive.

In some instances it may be desirable to drive the drag roller 20 as shown in the modified form, Figure 2, instead of driving pull roller 13. Drag roller 21 is driven through frictional contact with drag roller 20. The differential gear train 22 through output shaft 24 drives roller 14 and through frictional contact, roller 13. Throttle valve 55 as previously described for Figure 1 will control rollers 13, 14. The tension on web 11 tends to revolve rollers 20, 21 so that some of the power required to produce tension between rollers 13, 14 and 20, 21 is actually put back into the system. The arrangement 4 of Figure 2 is advantageous only when the weight of parent roll 12 is sufficient to produce added tension to the web 11. In Figure 2 the tension between rollers 13, 14 and 20, 21 is independent of the tension between rollers 20, 21 and parent roll 12, since rollers 20, 21 are driven by motor 15 and thus in effect feed web 11 to rollers 13, 14.

Having shown and described preferred embodiments of the present invention, by way of example, but realizing that structural changes could be made and other examples given without departing from either the spirit or scope of this invention, what I claim is:

1. A hydraulically controlled differential web tensioning mechanism comprising a web supply roll, a take up beam, a pair of feed rollers for advancing the web from the supply roll to the take up beam, a pair of drag rollers between the bite of which said web passes from said supply roll to said feed rollers, said drag rollers being driven by the pull of the Web thereon, a differential. gear train having an input shaft, an idler shaft and an output shaft, means connecting said input shaft to said drag rollers, means connecting said output shaft to said feed rollers, a pressure fluid system consisting of a reservoir, a hydraulic pump, a hydraulic motor, a throttle valve, a conduit connecting said hydraulic pump with said reservoir, 9. second conduit connecting said hydraulic motor with said reservoir, a third conduit connecting said hydraulic pump, said hydraulic motor, said throttle valve and said reservoir, means connecting said hydraulic pump with said idler shaft, means connecting said hydraulic motor with said output shaft, said throttle valve controlling the torque output of said hydraulic pump.

2. A hydraulically controlled differential web tensioning mechanism comprising a web supply roll, a take up beam, a pair of feed rollers for advancing the web from the supply roll to the take up beam, a pair of drag rollers between the bite of which said web passes from said supply roll to said feed rollers, said drag rollers being driven by the pull of the web thereon, a differential gear train including a casing provided with hydraulic fluid, an input shaft, an idler shaft and an output shaft rotatively mounted in said casing, means connecting said input shaft to said drag rollers, means connecting said output shaft to said feed rollers, a fluid pressure system consisting of a hydraulic pump, a hydraulic motor and a throttle valve, a conduit connecting the hydraulic pump with the hydraulic fluid in the casing, a second conduit connecting the hydraulic motor with the fluid in the casing, a third conduit connecting the hydraulic pump with the hydraulic motor and the throttle valve and the hydraulic fluid in the casing, the hydraulic pump being operatively connected with the idler shaft, the hydraulic motor being operatively connected to the output shaft, the displacement of the hydraulic pump being greater than the displacement of the hydraulic motor, the difference in displacements passing through the throttle valve and thereby controlling the torque delivered by the hydraulic pump to the idler shaft.

3. A mechanism as defined in claim 2 being further characterized in that; a parent roll is 'provided from which a web is withdrawn, a pair of drag rollers between which the web is passed in frictional contact, an axle supporting one of the drag rollers having a bevel gear fixed thereto, said input shaft having a shaft extension secured thereto and being provided with a pinion gear meshing with said bevel gear, an electric motor, a beam upon which the web is wound operatively connected to said motor for rotation, a pull roller operatively connected to said motor for rotation, a second axle provided with a bevel gear, a second pull roller fixed to said second axle and frictionally engaging said first mentioned pull roller, the web passing between said pull rollers in frictional engagement, said output shaft having an extension secured thereto and being provided with a pinion gear meshing with said last mentioned bevel gear.

4. A mechanism as defined in claim 3 being further characterized in that; the speed of rotation of said bydraulic motor is limited to second pull roller.

'5. The combination, of pull rollers frictionally engaging said web for moving said web, a pair of drag rollers frictionally engaging said web and being rotated by said web, a differential gear train including a casing provided with hydraulic fluid, an input shaft, an idler shaft and an output shaft, all shafts being rotatively mounted in said casing, means for connecting said input shaft to one of said drag rollers, means for connecting said output shaft to one of said pull rollers, a fluid pressure system consisting of a hydraulic pump, a hydraulic motor, a pressure gage and a throttle valve, a conduit connecting said hydraulic pump with said hydraulic fluid, a second conduit connecting said hydraulic-motor with said hydraulic fluid, a third conduit connecting said hydraulic pump, said pressure gage, said hydraulic motor, said throttle valve and said hydraulic fluid, means for connecting saidhydraulic pump with said idler shaft, means for connecting said hydraulic motor with said output shaft, an electric motor, means for connecting said electric motor with one of said pull rollers, the displacement of hydraulic fluid by said hy-' draulic pump per unit of time being greater than the displacement of hydraulic fluid by said hydraulic motor per unit of time, the excess displacement of fluid passing through said throttle valve, the displacement of hydraulic fluid of said hydraulic motor being determined by the speed of said electric motor, the throttle valve controlling the torque output of said hydraulic pump and thereby the torque applied to said idler shaft which controls the the speed of rotation of said with a web of material, of a pair torque exerted on said input shaftand thereby the drag applied to said drag rollers, the tension on said web between said drag rollers and said pull rollers being determined by said throttle valve and the relative value of the tension being shown on said pressure gage.

6. The combination, with a web of material of a first pair of rollers frictionally engaging said web, a second pair of rollers frictionally engaging said web, said web being tensioned between said first pair of rollers and said second pair or rollers, an electric motor, means connecting said motor with one of said rollers for imparting movement to said web, a differential gear train including a casing provided with hydraulic fluid, an input shaft, an idler shaft and an output shaft, all shafts being rotatively mounted in said casing, means for connecting said input shaft to said first mentioned pair of rollers, means for connecting said output shaft to said second pair of rollers, a fluid pressure system consisting of a hydraulic pump, a hydraulic motor, a pressure gage and a throttle valve, a conduit connecting said hydraulic pump with said hydraulic fluid, a second conduit connecting said hydraulic motor with said hydraulic fluid, a third flconduit connecting said hydraulic pump, said pressure gage, said hydraulic motor, said throttle valve and said hydraulic fluid, means for connecting said hydraulic pump with said idler shaft, means for connecting said hydraulic motor with said output shaft, the displacement of hydraulic fluid by said hydraulic pump per unit of time being greater than the displacement of hydraulic fluid by said hydraulic motor per unit of time, the excess displacement of fluid. passing through said throttle valve, the displacement of hydraulic fluid of said hydraulic motor being determined by the speed of said electric motor, the throttle valve controlling the torque output of said hydraulic pump and thereby the torque applied to said idler shaft which controls the torque exerted on said input shaft and thereby the drag applied to said first mentioned pair or rollers, the tension on said web between said drag rollers and said second pair of rollers being determined by said throttle valve, the relative value of the tension being shown on said pressure gage, the power to produce the tension on the web being transmitted directly from said input shaft through said differential gear train to said output shaft and the power being transmitted indirectly from said input shaft to said output shaft through said hydraulic pump said differential gear train and said hydraulic motor.

7. A hydraulically controlled differential web tensioning mechanism comprising a differential gear train including a casing provided with hydraulic fluid, an input shaft, an idler shaft and an output shaft rotatively mounted in said casing, a fluid pressure system consisting of a hydraulicpump, a hydraulic motor and a throttle valve, a conduit connecting the hydraulic pump with thehydraulic fluid in the casing, a second conduit connecting the hydraulic motor with the fluid in the casing, a third conduit connecting the hydraulic pump with the hydraulic motor and the throttle valve and the hydraulic fluid in the casing, the hydraulic pump being operatively connected with the idler shaft, the hydraulic motor being operatively connected to the output shaft, the displacement of the hydraulic pump being greater than the displacement of the hydraulic motor, the difference in displacements passing through the throttle valve and thereby controlling the torque delivered by the hydraulic pump to the idler shaft, a parent roll from which a web is withdrawn, a pair of drag rollers between which the web is passed in frictional contact, an axle supporting one of the drag rollers having a bevel gear fixed thereto,

the web is wound operatively connected to said motor for rotation, a pull roller operatively connected to said motor for rotation, a second axle provided with a bevel gear, a second pull roller fixed to said second axle and frictionally engaging said first mentioned pull roller, the web passing between said pull rollers in frictional engagement, saidoutput shaft having an extension secured thereto and being provided with a pinion gear meshing with said last mentioned bevel gear.

8. In a web tensioning mechanism, a pair of drag rollers, a pair of driven rollers, a differential gear train with three power transmitting shafts, a pump, a motor, a hydraulic system connecting said pump and motor, a driving connection between the first of said three shafts and said pump, a driving connection between the second of said three shafts and said motor, a driving connection between the third of said three shafts and said drag rollers, and a driving connection from said driven rollers to the second of said three shafts.

9. A web tensioning mechanism comprising a web supply roll, a take up beam, a pair of feed rollers for advancing the web from the supply roll to the take up beam, a pair of drag rollers for applying a tension on said web during the advance thereof from said supply roll to said take up beam, a differential coupling between said pairs of rollers, a fluid pump adapted to be driven by the differential for applying a torque thereon to control the rotation of said pair of drag rollers, an hydraulic motor connected to said pair of feed rollers, the output of said pump being connected to said hydraulic motor, and valve means for controlling the output of said pump to said hydraulic motor.

10. A web tensioning mechanism comprising a web supply roll, a take up beam, a pair of feed rollers for advancing the web from the supply roll to the take up beam, a pair of drag rollers for applying a tension on said web during the advance thereof from said supply roll to said take up beam, a differential coupling between said pairs of rollers, a fluid pump adapted to be driven by the differential for applying a torque thereon to control the rotation of said pair of drag rollers, and an hydraulic operated motor coupled between the output of said pump and said pair of feed rollers adapted to be driven by the said output of said pump.

11. A web tensioning mechanism comprising a web supply roll, atake up beam, a pair of feed'rollers for advancing the web from the supply roll to the take up beam, a pair offdragrollers for applying a tension on said web during the advance thereof from said supply roll to said.take up beam, a difierentialmechanism having three rotatable members, the first offsaid members being coupled to said drag-rollers of said members being coupled to said feed rollers for rotation therewith, said first and second members rotating at different velocity, a fluid pump adapted to be driven from the third said member in response to the difference in velocity of the said'first and second members for applying a torque onsaid differential opposing the rotation of said drag rollers, andvalve controlled means coupled to the outputof' said pump and' said feed rollers for transmitting torque from said pump to said feed rollers.

12. A web tensioning mechanism comprising a, web" supply roll, a take up beam,ra pair of feedrollers for advancing the web from the supply rollvtothevtake up beam, a pair of drag rollers for applying a tension on said web as advanced from said supply roll,,a constant power source for driving said feed rollers, said drag;

rollers being driven by the pull of. the web thereon, a differential mechanism havinga first rotatable member connected to said pair of drag rollers and rotatable thereby, a second rotatable member connected to saidv pair of feed rollers, a third member connected 'to the saidfirst and second member and through which motion is transmitted from the first said member tovthe said second. member, an hydraulic motor connected to said pairiofieed rollers, a fluid pump connected to said thirdfmembenand driven thereby for applying a torque on saidthir'dmember, means connecting the output-side of. saidpumpflo said hydraulic motor, anda valve-means for.t controlling the output of said pump to said hydraulic motor.

and rotatedthereby, the second 131 A web tensioning mechanism comprising a web supply roll, a take up beam, a pair of feed rollers for advancing the web from the supply roll to the feed rollers, a pair, of drag rollers positioned between the supply roll and the said'feed rollers for applying a tension on said web during the advance thereof from said supply roll to the take up beam, drive means coupled to one of said pair of. rollers for driving the same, the other of said pairs of rollers being driven by the pull of the web thereon, a

References Cited in the file of thispatent UNITED STATES PATENTS 1,563,452 Stoltz Dec. 1, 1925 1,855,222 Chase Apr. 26, 1932 1;881,056 McBain Oct. 4, 1932 1,949,237 Bradner Feb; 27, 1934 2,164,596 Simonds July 4, 1939 2,168,071 Perry Aug. 1, 1939 2,392,226 Butterworth et al; Jan. 1, 1946 2,599,795 White June 10', 1952' FOREIGN PATENTS 450,488 Great Britain July 10, 1936 OTHER REFERENCES Popular Science, April 1954, pages 146, 278. 

